Process of removing deterrent salts from pickling liquors



Patented May 3, 1927..

UNITED STATE-s v l 1,626,623 PATEN OF IC eaonen s; MORGAN, or 'roLnno, 01:10. 3 I

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No Drawing.

My invention has-for itsvobject. provide a process for removing the iron salt or compound from pickling liquor which 18 .pro-

uced in the pickling of iron and restoring it to 1ts orlglnal 'rustremovlng effectiveness.

As 1s well known In connectlon with iron pickling process sulphuric-acid is used to reacid of the exhausts move the rust. This producesv ferrous isulphate in the acid solution by the action of' solution is restored by removal of the ferrous sulphate.

Processes containingfmy invention may .varied as to the ste staken and as to the proportion of the e ements of ingredients that are treated or are added to the solution of mixture, in connection with which the process containingmy invention, -is performed. A preferred form of a process containing my invention is selected as an ex ample of such process and is described hereinafter. j 1

, The invention primarily has for its objects to enable the use of all ofgthe sulphuric acid introduced in pickling solutions and to re cover the ferrous sulphate produced by the action of the acid on the rust, This is done by the precipitation of the ferrous sulphate by the use of a solution of sulphuric acid.

The solution is increased in its acid content until the concentration is from 35% to Fresh pickling lirglior for removing rust is-usually water-aci 'fied with .6% to 10% sulphuric acid and is used until the ferrous sul hate that is formed by theaction of the aci on the ferrous oxide amounts to about 5% to 15% of the solution, and the free acid is reduced to 1% to 5% of the solution. Usually the solution is considered exhausted when the ferrous sulphate amounts to about 12% and the acid is about 3%. In order to restore the exhausted solution a considerable amount of acid is added to the solution to cause a precipitation of the ferrous sulphate. Prefera ly enough acid is added to make Applicationflledjune 30, 1926. serial l io. 119,747;

a 50% solution by wei ht. f As foriexample,

to 100 pounds of pick i'ng: liquor about 100 pounds of acid at about '66 degree-Baum, or its equivalent in any strong sulphuric acid-- is used, that is, a greater weight-ofthe acid Wlll be used where the specific gravity is less. This; causes practically all of the fer- "rous sulphate to precipitate a white 'anhy drous form.

As ,to the acidity of the solution where it is changed from the 3% to; 50% a slight cloudy effect will begin to form when the acid solution becomes a 35% solution and the ferrroussulphate begins to come down very noticeably at slightly above 35%. Practi cally all the ferrous sulphate will be precipitated when the acidity reaches that of a 50% solution. v y

The precipitate is allowedto settle and the clear acidified liquor is runjofi havingv p'ractlcally .no ferrous sulphate dissolved" therein at least not to'exceed 1% where a 50% acid solution is formed. The ferrous 'sul hate contained in -the solution will not or inarily exceed a verysmall fraction of 1% of the. solution.

The 35% to 50%, or thereabout acid solution that is drawn-from the precipitate may I be stored for further use, or water'may be added thereto to reduce the acid content toabout 10% and the solution used for pickling purposes until-the'solution is exhausted, that is, until the acid content is" reduced to about 3%, and the solution contains about 12% of ferrous sulphate. Thus inacontinuous use of the pickling solution all of the acid is consumed to form the ferrous sulphate which is separated from the pickling liquor as described. H

When the 35% to 50% acidifiedWateris drawn from the preci itated; ferrous sulphate, the ferrous sulp ate will hold some of the acid mechanically mixed therewith andapastelikematerialisformed. Thepaste like material is laced on a suitable vacuum filter to hasten th therewith. I

Also thegprecipitated ferrous sulphate is e separation of the precipitate' from the liquor mechanically mixed 165' preferably washedqgvith an exhausted ortion of the pickling; liquor, that is, picking liquor that has ferrous sulphate to a concens trated degree and is low in acid, to remove the excess acid mechanicall mixed with thepreci itate. Since the pic ing liquor with vwhic a precipitate is washed is low inacid rous sulphate. This is then allowed to coolwhen the copperas ,will crystallize out. Thus.

and high in ferrous Sulphate but little of the precipitate will be dissolved. The precipi:

tatethat is left-ma bedried and used ori I any purpose for 'w ich lanhyd-rous ferrous sulphate may be used.

pickling liquor which will dissolve the fer-' not only theferrous'sulphate that was introduced into-thesolution is removed, but also some ofthe ferrous sulphate that wascontained in the solution into Whichthe '2. precipitate was dumped is also removed.

of the The mother liquor may be drawn ofi from reachesa out 20%. The proces maybe conducted continuously, that is, by a continuous flow of the solutionsand if deSired'Storage of portions thereof. A Q

Iclaim: I v

The process of removing'jdet'errent salts from pickling solutions for iron which consists in precipitating the iron sulphate by adding sulphuric acid to the solution until the acid content amounts to about 35% to 50% of the solution, drawing oil the liquor and dissolying the precipitate in hot exhausted pickling liquor, cooling the solution to formlcopperas.

In testimony whereof. I have hereunto signed my name to this s ification. GEOR S. MQRG AN.

the copperas and used for dissolving; more recipitate until -its acid content Cil- 

